Semi-autonomous sensory-motor control for upper limb prostheses

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In the past decades, efforts have been made to establish man-machine interfacesbetween prostheses and the human nervous system [1]. These interfaces have providedsome level of control and, in rare cases, the possibility to transmit some sensation to theusers. Nonetheless, clinical translation of advanced bidirectional sensory-motor controlinterfaces has been limited. An ideal prosthetic device should mimic the sensing and actuation capabilities of thebiological counterpart. Considering the sophisticated structure and neural control ofhuman limbs, this is an extreme challenge. While the mechatronic technology has beendeveloping rapidly in recent years, allowing us to come close to this ideal, the informationtransfer between the prosthesis and the user offered by state-of-the-art man-machineinterfaces is still extremely low. Even advancing the interfacing technology, it is veryunlikely that neural interfaces can replicate all aspects of natural sensory-motor control. While the prosthesis cannot be fully neurally "re-connected" to the user to exploit theirdecision-making and sensory/control abilities, it is possible to enhance the device with itsown intelligence. This approach is a radically different conceptualization of an assistivesystem with respect to current state-of-the-art, promoting the robotic controller from asimple decoder of the user intent into an intelligent agent collaborating with the user inaccomplishing functional tasks. Within this approach, the user transmits information onlyabout a high-level goal (e.g., grasping a cup) while the details of the movements (e.g.,specific approach trajectory, grasp type and size) unfold mostly subconsciously, mimicking thereby how healthy subjects control their limbs. The sensory-motor control wouldtherefore become semi-autonomous, as for most natural tasks that are executed withoutconsciously controlling all the body degrees of freedom and integrating sensory feedback.The semi-autonomous approach to prosthesis control has been preliminary exploredmainly in relation to the motor part of the sensory-motor loop (e.g., from our researchgroup see the recent paper [2]) while semi-autonomous full sensory-motor loops havenever been explored in prosthetic systems. In this project we propose the development of a semi-autonomous control system forprostheses that integrate motor commands with sensory information in closed-loopsystems both at the user level (conscious sensory-motor control) and at an AI agent level(autonomous sensory-motor control). These two sensory-motor loops share the task ofthe ultimate activation of the prosthesis.